Current silicon-based (Si-based) CMOS-compatible electro-optic modulators generally have response bandwidths (i.e., 3 dB bandwidths) that are limited to a few gigahertz (GHz), at best. Traditional devices also have uneven responses wherein the time required to activate the device is very different from the time required to deactivate the device. These devices have traditionally relied on carrier injection into the optical waveguide to create effective optical refractive index changes. This requires a voltage bias to be applied to the device, wherein DC power consumption results.
Response speed for these devices is also limited, since carriers have to traverse the entire distance between ohmic contacts of the device in order to activate and deactivate the device. This action occurs because the response speed of the device, in the forward-biased state, is limited by the diffusion speed of the carriers across the intrinsic region of the device. Additionally, current devices have severe bandwidth limitations and incur relatively large optical losses corresponding to changes in their optical refractive index.
Accordingly, what is needed in the art is an enhanced design that overcomes some of the limitations of the current art.